1208 Wisconsin Academy of Sciences, Arts, and Letters. 
fusion really takes place or not, as in both species the nuclei are 
so exceedingly small. The mature spore, however, is uninucle- 
ated and its cytoplasm frequently contains very large vacuoles 
while the nucleus is pushed to one side. 
In all essentials the mycelium and spore formation of TJ. 
Zeae will be seen to be the same as that of U. levis. The vege¬ 
tative mycelium, composed of multinucleated cells, breaks up 
into short segments containing one or two nuclei which pass into 
the spores. In both species it is impossible to determine 
whether two nuclei are always present in these segments or 
whether they fuse to form the one nucleus which appears in the 
mature spores. 
Fusions in the Promycelial Cells of Some of the Smuts. 
The spores were germinated in drop cultures on slides placed 
on racks in damp chambers. The material found best for this 
purpose was an exceedingly dilute beer-wort. An addition of 
even a few drops of beer-wort to a watch glass full of water was 
sufficient to help the germination of the smut spores and not suf¬ 
ficient to cause much immediate growth of moulds. The food 
material being so dilute was soon used up and the promycelial 
cells started almost immediately to fuse in pairs. These cul¬ 
tures could be kept without drying out or without so very much 
contamination for a week or ten days which was as long as it 
was necessary to obtain material at all stages of development. 
The spores of U. hordei, U. A venae, and U. Tritici were used 
for this germination and all showed practically the same results. 
The promycelia were stained on the slide directly by means 
of a modification of the method proposed by Harper (22) : A 
slide was rubbed with albumen fixative as for sections, one of 
these cultures was pipetted on it and the Flemming’s weaker 
solution added. The fixing fluid coagulated the white of egg 
and the spores and promycelia stick in it after the drop is al¬ 
lowed to dry out. After bleaching in hydrogen peroxide the 
slide was stained in iron-haematoxylin or the triple stain. 
Under the above conditions the promycelial cells fuse in pairs 
almost as soon as formed; there is sometimes a fusion in threes 
